Isıl Etkiye Maruz Kalmış Granit Ve Mermer Örneklerinin Fiziksel Ve Mekanik Özelliklerindeki Değişiminin Araştırılması

Abstract

One of the factors affecting physical and mechanical properties of rocks is temperature. This effect, which is called thermal effect, manifests itself in the applications of field of geo - engineering such as geological repositories for radioactive wastes, underground gasification of coal, geothermal energy, deep underground mining where rocks are subjected to high temperatures, and in the form of tempera ture increases in stone buildings which subject to fires. In studies related to the first type of thermal effect mentioned above, rock samples are heated until the desired temperature is reached and then physical and mechanical properties are determined un der this temperature. This application requires expensive and more sophisticated test devices and there is limited number of study on this kind of thermal effect. In the assessment of the other thermal effect, which represents fires, by considering the con ditions after fires, changes due to temperature are evaluated on the specimens which were first subjected to heating and then allowed to cool down to room temperature. Although the number of studies based on this approach is greater, in our country, ther e is limited study, which were conducted on the variation of physical and mechanical properties of only a few building stones. By considering the above mentioned issues, in this thesis study, it was aimed to investigate the changes in the physical and mech anical properties of granite and marble samples depending on temperature based on a thermal effect occurred in iv the near past and to assess general trends and threshold temperature values associated with the changes in these properties by comparing the resu lts from this and previous studies. For these purposes, the specimens prepared from both rock types to be used in different tests were subjected to thermal effect under temperatures reaching up to 1000 o C, and then they were allowed to cool down slowly to r oom temperature. Main physical and mechanical properties of all specimens were determined and assessed, besides their stre s s - strain curves were also drawn t o evaluate their variations depending on temperature. In addition, porosity of the specimens was al so determined using X - ray CT method and the results obtained from this study were compared t o those obtained fr o m the previous studies with similar purpose. Based on the results of the study, except small fluctuatio ns, generally no evident change in the m ineral composition of the granite and marble specimens depending on the increase in temperature has occurred. For both rock types, except porosity, it is understood that all physical and mechanical properties showed a decrease with increasing temperature . Both granite and marble specimens show transition from brittle to ductile behaviour as temperature increases and this trend confirms the results of the previous studies. If the granite and marble, of which the values of slake durability index significant ly reduced with the increase in temperature, are subjected to a number of wetting - drying cycles in the field and then used as a building stone, the se materials would be adversely influenced by thermal effect resulted from fires. The values of porosity dete rmined from the X - ray CT method and the method suggested by ISRM are consistent until a certain temperature. The comparisons between the results of this study and those from the previous similar studies conducted on granites and marbles indicated that the physical and mechanical properties of the specimens subjected to thermal effect generally show a similar trend to those in the previous investigations. According to the values of threshold temperature, which were estimated from the average trend lines for different rock properties, the threshold value indicating that the granite specimens are evidently influenced by the increase in temperature is 400 o C, while it is 100 o C for the marble specimens.